Efficiency meter



Aug. 24, 1965 H. s. MORTON EFFICIENCY METER Filed Aug. 27, 1962 2 51 Jun. 20mm &

223m JMDm 20m.

INVENTOR HAROLD S. MORTON ATTORNEY United States Patent 3,201,978 EFFICIENCY METER T Harold S. Morton, 7331 Piney Branch Road, Takoma Park, Md.

Filed Aug. 27, 1962, Set. No. 219,542 11 Claims. (Cl. 73114) This invention relates generally to metering devices for comparing the rate of consumption or expenditure of a liquid input with the useful output resulting from such consumption or expenditure whenever the latter can be measured and expressed in terms of a rate of flow of the same fluid which measures the input; more particularly, it relates to an improved metering device for indicating the operating efficiency of a motor vehicle in miles per gallon rates of fuel consumption, instant by instant during the operation of said vehicle.

For various reasons it is desirable to know at any given instant during the course of their operation the efliciency in terms of miles per gallon of fuel consumed of automobile and like vehicle engines. Numerous devices have been proposed for measuring this operating efliciency,'but most have suffered from one or more faults which have rendered them undesirable in actual use.

A common problem with efliciency measuring devices for this purpose hasbeen their inability to compensate for changes in fuel viscosity occurring because of variations in fuel temperature. In some prior meters the device is capable of measuring efliciency accurately at the fuel temperature for which it was designed, but furnishes a reading that is substantially in error for other significantly different fuel temperatures. Because fuel temperature often varies greatly in actual conditions of use, due to weather changes and other factors, an

eificiency meter free from the effects of such varying temperature is obviously desirable.

The efliciency meter of the invention compares two rates of fluid flow to obtain directly the operating efficiency of the'vehicle engine to which the fuel is being supplied. Because both rates of flow are taken from the same body of fluid, variances in the fuels temperature and viscosity do not affect the accuracy of the meter. Thus, the problems of past devices associated with both varyingtemperatures and varying viscosity are overcome.

In addition to eliminating the effects on the accuracy of the meter readings of variations in temperature and viscosity of the fluid flowing through the metering device, the present invention also eliminates the effects on the meter of gravity and of accelerations of the vehicle in any direction. This is accomplished by making the single moving element of the present meter identical in density with that of the fluid in which it is immersed.

The most usual manner for expressing the operating efficiency of'a vehicle engine is in terms of the miles per gallon of fuel consumed. It is desirable that an efficiency meter be capable of furnishing readings directly in these terms, and that accurate readings be continuously avail able during operation of the vehicle. Some past efficiency measuring devices have lacked the first of these two capabilities, and many have lacked the latter. The efficiency meter of the invention possesses both capabilities.

It is, therefore, an object of this invention to provide an efliciency meter capable of continuously determining during its operation the operating efliciency of a fluid fuel engine.

Another object of the present invention is to provide 3,201,978 Patented Aug. 24, 1965 a vehicle engine operating efficiency meter so constructed as to be unaffected by gravitational and acceleration forces acting thereon.

A further object of this invention is to provide a meter for determining the operating efliciency of a fluid fuel vehicle engine, so constructed as to be independent of the temperature and viscosity of the fluid fuel.

It is also an object of the subject invention to provide an operating efliciency meter so constructed as to indicate directly in miles per gallon of fuel consumed the operating efliciency of a vehicle engine.

An even further object of this invention is to provide a vehicle engine operating efficiency meter that is relatively insensitive to sudden pressure disturbances in the flow of fluid therethrough.

Still another object of the present invention is to provide a calibrating device for a vehicle engine operating efiiciency meter, so constructed as to permit accurate calibration and adjustment of said meter for operation with any 'of several different vehicle and engine combinations. f

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same become better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

FIG. 1 is a schematic view in axial'section of a first embodiment of the invention; and

FIG. 2'is a schematic view similar to FIG. 1 of a second embodiment of the invention, showing the surge damping orifice structure and the meter calibrating plug assembly thereof.

The efliciency meter of the invention utilizes the lami- L nar flow characteristics of fluids, at Reynolds numbers below 2000, for indicating the operatingefficiency of a fluid fuel vehicle engine continuously during operation. While the invention Will hereinafter be described with reference to a gasoline automobile, it is to be understood that it is notto be limited to such use. The meter of the invention can be readily utilized with engines utilizing fuels other than gasoline, and with vehicles other than automobiles. Moreover, its use is not necessarily limited to vehicle engines, but may extend to industrial power plants and, in appropriate instances, to certain chemical processing equipment Where a definite measurable output of material is produced in proportion to a fluid input.

The meter of the invention consists of an elongated housing containing therein two spaced, aligned bores'each having a discrete length. 'A plug is mounted concentrically within said bores for nearly frictionless movement, and includes two identical in diameter, enlarged cylindrical end portions of unequal length connected by a reduced shaft, each cylindrical plug end defining with the wall of its associated bore an annular flow space. A pair of fluid inlets are positioned centrally of the housing between the two spaced bores,'one for admitting to the meter fluid passing from the fuel tank to the engine and the other for admitting fluid being recirculated by a positive displacement pump. One end of the housing has a fluid outlet positioned adjacent the end of the cylindrical bore within which the longer of the two enlarged plug ends is disposed, and the opposite end of the housing has an outlet which communicates the other bore with the intake of said recirculating pump.

In operation liquid fuel from the vehicles supply tank is delivered to the meter, usually by the fuel pump of the of the invention. r a I 7 a The end walls-30 and 32 of the housing-2 have bores engine, at exactly thesame 7 way to the engine, the fluid being drawn past the longer of the two plug ends as it passes throughthe meter;

When the vehicle is at rest this is the only flow through I the meter, and consists only of the fuel being used by an idling engine not moving thevehicle; Under these conrate it leaves the meter on'its The metering'plug 44' includes arelativelyt long; en-

. larged cylindrical end portion'46, a relatively short cylin- -drical end portion 48, and a reduced in diameter conditions the entire plug, being freely suspended in the meter, moves as far as it can in'the direction of the fluid flowtherepasth y Y, H i s .soonasthe vehicle begins to move, .the recirculating pump, which is activated by motion of the .vehicle c om jmen'cjes operation; the, vpurnpi draws tgflu'id; fuel. past. the

shorter end of theplug 'a't a riate proportionalito the speed ofthe, vehicle,;and returns :it to the center of the-meter.

The flow of fluid past the shorter,plugrendreXertsa force' counter to that: exerted, by the How :of fuel going to: the i necting shaft50, and has a cylindrical bore 52 extending completely therethrough of a size to freely receive rod 40, said bore being positioned concentrically within the plug. 7 Suitable bearing .means (not) shown) are fitted within the "opposite ends of thefbore 52 whereby to permit the substantially frictionless movementof said plug on said rod. a I I .r r

The-plug end portions'flfi and48 have identical diamete'rs, which'di'amet'ers airersomewhatile'ss' than the diameters of tube bores 24 andz' stwiieteby annular flow spaces,

nor channels, 'Ojand R; respectively,are-defined between engine pastthe longerend ofthe-Epl u'gnwhich longer end hasonlya portion of itSJengthEWithinits enclosing bore]; inv the meter housing. The plug is free to move, and

does so until the two forcesiareperfectly equalized/at a plug positionwdetermined ,by the relative'frates.v Orianaflow'past the two ends of-the plug, one flow being the actual fuel consumedand'the. other being directly proportional to; the ivehicle, rate of-qimotion which; use of; the,

consumed fuelproduces. r

Thepositio ,vOftheplug whenjthe two:forcesigenerated byannularfluidlflow from 'thejcenterofthemeter toward the, endsitherejof exactly balance oneuanotheriis a direct J3 indicationof theefficiency, measured'in miles per-gallon} t at any instant, The variation in plu'g-positionresults from the adjustment. of the annular-flowzpassage throughzwhich the fuel 10 e consumed flowsibyyaryingthe effective length ofltheilongerjplug end relatiiveto its surrounding housing bore, said length being varieduntilthegforce prof duced bythgflow j of fuel to ther enginejjust balancesthe force resulting from fuel-recirculationiat a rate proper; tional tovehiclegspeed through-the fixedintlength annular passage between the shorter plug end and its surronnding housingjbpre'; Thus, :bypmeasuiing, the position. of,the plug at any instanta direct indication'offefficiencyat. that instant in terms of milesper gallonof fuel"consumedcan v be obtained; r

l R riu i now s'aidplug end portions-anditheir respective surrounding ube'wa i-Ty al w h lca r end rt on 2 t m e an wi t e ls th t f n q t n ma hin having a length w'aboutg'the same'as saidf e'nd portion 4 6 The tube 16' is; sufficiently long an d is so positioned a s smit ream L. 9? nd P rt 4 w s ..QI1-. t in th i nto r th ent r a er, m vem Qf'pn 44,- which' range is limited bytstop slg5 4 bu ;rod 40 and EXj i ten s: om airin iti vh l inrth entire length of 'tube22 isoccupied by; en

said ping is-shifted to the le of plu'giendflfiis disposed withinsaid tube 22.;

T .me fthe v n o fld cndem r itsv pe' ar t n- 91 91 the la in -fle har e is ic of h fl i f fluid -wrench a ne, an, nu r or o hcre w shann l 9t nifcrm ewe-s ion e e v ty v. h fl id 19W i i re y' P opo tional o t e: pr s e; fqriqnt a betwse l tncs t v th h mheni nd' i versely proportionalto the lengthofthe. flow channel and to the, kinematic viscositygoffthe; fluid.- The quantity of 1 fluid ppassing; hrou'gh a; channel having laminar flow is directly-proportionalto the cross-sectional area of said channel and, tfo the pressure ,difierential -between :the two shownschematically'injFIGr- 1, a housingistindicated. at

2 and includes in axially alignedfrelationship,'a fuel outlet chamber 4,- a firstreduced cylindrical chamber; 6, anren-i V larged inlet, chamber 4,-,:a second reduced. cylindrical chamber 10, and a recirculating fiuid outlet chamber 12.

7 An internally threaded fueloutletnl'4 communicate's'fcham-E beryl with the exterior of the meter, a pairiof similarly constructed inlets 11 6flan'd l8 are in communication with a cylindrical tube22 having an internal bore'24 which "isof uniform diameter throughout its len'gth,1a' similar tube 26 beingfitted within chamber ltl'and having aiunifornr bore 2 8 -therethrough, tha-t is videntical in diameter vwith bore 24. The tubes22 and 26 havetthe-sar'ne central aiiest and are secured within thejhousing :by any suitable means, it being understood. that while, in the. schematic drawing the housing 2 is indicated asibf ing of oneipiecei't would necessarily in" an;actual embodiment. b'e composedofi a' plurality iof' secured togethepelements, wh'er'eby to make I v A; he'cross sectio' al area of the flo I 'P 'the-pressure differential between the ends of the flow chamber 8,'and, a recirculatin'glfluidoutlet Z Dis' in 'com munication withchamber 12.; Fitted with chamberois v V v r q '1 aslf o llowsr' to the embodiment of thegin'ventiOn I I J where:

lsthelength of th e fiowchannel (1111)";

ds ths i qfir and inversely r p ion tQ- he en thio thefch'annelandto the kinematic iscosityof the fiuid. Expressed mathe'mati cally,"theaabove relationships are V=the kinematic visc osityfjof the fluid ing/hour) and T k '=a constant related to',dimensi0nal' characteristics of the channel'through which laminar fl'ow is occurring. the meter-of F IGQlthere are two flow channels both 7 "of which are. proportioned injthej .iknown manner, for

laminar fluid flow; the annular channel Olaround fplug end46,; throngh'whichfuel flows to the carburetor of the engine, and the annular channel, R around plug end 48, through which fluid flows to the inletvof a positive displacement, recirculating :pump 56 connected ,withoutlet 20. The areaof the tfirstfchannel may-conveniently be possibletheassembly of componentszthereinto, 'I'he'mannerpf fabricating such housings from afplurality of ele} ments is well known,. and henceisnotconsidered apart;

34 and 36' therein, tsaid bores being concentrically "dis posed-about the centerline-of tubes-22' and,26} Ari elec trical insulating bushing 38 is positioned within 'ea'ch 'of said bores, and the oppositethreaded endsofa cylindrical.

metering plug '44.

supportrod extend through saidbushings and are. s.e-. cured in position by nuts 42; Mounted onrod 40 is a 1 n flow channel Ovarieshs the 'plfig tt. moves, and desig- R, 'as', follows;

"gators, I

where:

Q Q =the rates of flow through channels 0 and R, re-

spectively (gallons/hour);

A A =the cross-sectional areas of the flow channels 0 and R, respectively m2 P P =the pressure differentials between the ends of the flow channels 0 and R, respectively (1bs./in.

X, L=the lengths of the flow channels 0 and R, respectively (in.);

V V =the respective kinematic viscosities of the fluids flowing through channels 0 and R (in. /hour); and

k k =a constant related to the respective dimensional characteristics of the channels 0 and R.

The embodiment of the meter shown in FIG. 1 is intended for use with an automobile, and fluid fuel is pumped into said meter through inlet 16 from the automobiles fuel tank by a conventional fuel pump, the volume of fluid flowing into the pump being determined from the power output demands made on the engine; from inlet 16 fuel flows through flow channel 0, into chamber 4, and then to the automobiles carburetor through outlet 14. The meter of this invention is intended to indicate the operating efficiency of the automobile in terms of miles per gallon of fuel consumed. The operating efliciency, or fuel economy, in the invention 2 may be expressed mathematically as:

S 4 Qio where: E=the automobiles instantaneous operating efliciency (miles/ gallon) S=the value of the automobiles speed at the instant for which E is being determined (miles/hour); and Q =the rate of flow through channel 0 at the instant for which E is being determined (gallons/hour). The recirculating pump 56 in the embodiment of FIG. 1 is of the positive displacement type, and is driven from the automobiles road wheels at a rate proportional to the speed of the automobile. The pump 56 may be a gear pump or any other commercially available type, and delivers a definite volume of fluid for each revolution of the automobiles wheels. It is driven by the motion of the automobile through a suitable connection with the wheels thereof, preferably through a take-ofl? from the drive shaft or transmission similar to that utilized for driving the speedometer. The output of the pump is connected to inlet 18, and fluid thus flows from chamber 8, through channel R and into chamber 12, out of said chamber 12 and through pump 56, and thence back into chamber 8. Thus, a recirculating flow is established which is available as a measuring standard.

Referring now to Equation 4, it can be shown that:

that:

Qio=Qo QiR QR Substituting into Equation 4 the relationships of Equations 2, 3, 5, 6 and 7, it is now apparent that:

QiO 223 O O O R- Referring now to FIG. 1, it is seen that because the bores 24 and 28 are of the same diameter, as are the plug ends 46 and 48, the cross-sectional area of flow channels 0 and R are identical. Thus,

Fluid entering into chamber 8 has a pressure which in the drawing is indicated as P The fluid at a pressure P flows through channels 0 and R into the chambers 4 and 12, within which chambers the fluid pressures are obviously at lower levels than in the chamber 8 because of losses incurred in flowing through said channels. Because the plug 44 is free to move, if the pressure within chamber 4 should vary in the slightest from the pressure in chamber 12 the plug will shift until the pressures in said chambers are equal. It is thus evident that once plug 44 has shifted pressures in chambers 4 and 12 are identical, which pressures are identified as P in FIG. 1. From this relationship it is apparent that:

The kinematic viscosity of a fluid is known to vary with the temperature thereof. This variation of viscosity with temperature creates, as described hereinabove, an accuracy problem when two separate bodies of fluid are being compared. In the instant invention, however, the fluids flowing through both channel R and channel 0 are from the same body of fluid; thus, they have the same temperature and kinematic viscosity. Therefore, it is seen that:

As has already been specified, the two flow channels 0 and R are identical in dimensional characteristics. This establishes the following relationship:

Substituting the relationships of Equations 9, 10, 11,

12 and 13 into Equation 8, and cancelling where appropriate, it is now seen that:

From Equation 14 it is seen that for the meter shown in FIG. 1 the operating efiiciency, or fuel economy, of an automobile engine with which the invention is utilized is proportional to the ratio of the variable length X to the fixed length L, multiplied by the constant M. Because of the construction of the meter such variables as fuel temperature and viscosity are immaterial, the advantages to be gained thereby being readily apparent.

The constant M, which for use with an automobile is defined as the number of traveled miles required to pump one gallon of fuel through the annular channel R, should be chosen so that the highest E that the automobile can obtain will not exceed the maximum value of X resulting when the plug moves as far to the right as is possible. Thus, by utilizing various values for M the meter of FIG. 1 can be employed with engines of varying operating efficiencies. H

As has been described, the pump 56 is of the positive displacement type, and for use in an automobile it is conventionally connected into the power train so that each revolution of the automobiles driving wheels will pump a specific volume of fluid through channel R. The value for M is thus directly dependent upon the capacity of the pump 56, and on the number of revolutions, or cycles, it completes per mile traveled. Correlations between the value of M and an expected range for values of E are best made by choosing a value for M which gives a midscale E reading. A midscale reading occurs when X and L are of equal length, in which instance, from Equation 14:

Thus, from Equation 15 it is apparent that if a midscale E reading of, say, 12 miles per gallon is desired, then a pump 56 should be chosen which will deliver one gallon of gasoline through the channel R for each 12 miles of automobile travel. Proper values of pump capacity, and revolutions thereof per mile established 'will-be moved'as far to the left as is possible.

7 V in the gearing connecting the pump to the automobile power train, can give this'or any other desired value for M.

Thus, with a fixed value forM, properly chosen for the expected range of E valuesQthevalue for E at any given instant can be readily determined fromEquation l4 by'theratio of 'X to L. Since the value-of L is a constant, the only variable in Equation 14 for a given Mis X. If the value of X is known, therefore, the value for E can be readily calculated.

In operation, fuel is admitted into the meter ithrough inlet 16 and enters chamber 8. r A portion thereof flows through channel to chamber 4 and thence, in automotive use, to the engines carburetor through outlet 14.

Assuming that the automobile is initially at a standstill and that pump 56 is therefore idle, there will be no fuel.

flowing through channel R,-and consequently plug 4 mittedto the meter, and will tend to reducethe drag effect of slide 68 and aid the plug 44 to move freely in response to changes in flow conditions. V

The movement of plug 44 might be expected to be affected ;byacceleration effects, on the meter, this problem beingespecially present in automotive application;

However, in'the construction of the invention this po- 'tential source of reading error is eliminated by making exist to cause motion'of the plugrelativetothe fluid surrounding it.

As the automobile moves, and; pump 56 commences t-ooperate, it will draw fuel' fr-om' chamber '8 through channel R, causing a momentary pressure differential between chambers 4 and 12; Plug 44 immediately move to compensate for this pressure difierential, stopping only when the pressures in chambers 4 and '12 are equal. The length X is then a measure of the instantaneous operating eificiency of the engine at that particularautomoe bile speed, and for that particular rate of fuel flow;

I As the fuel demands of the engine increase, oras the miles traveled per'hour by the automobile vary, pressure differentials will occur between the ends of plug44'. V The plug always. moves instantly to compensate for, these changes, causing lengthX toychange and thus furnishing an indication ofa new value for E for theznew operat- As has been described, the meter of FIG. 1 can be adjusted to measure a, variety of ranges ofvalues for E, it only being necessary-toyary the valueof the constant M for'each range of values by changing either the 'size of the pump 56 or therdriving gear therefor. However, it is obvious thatsuch changes are somewhat in,-

Jvolved mechanically," and that consequently the meter of FIG. IV'VIS not as flexible as might be desired for easy installation on a variety of different automobiles, for examplejeach ofwhich might have a diiferent-range of values forE. f Further, the construction of FIG. 1 does ing conditions. Thus, by constantly knowingthe value of X it is possible to obtain a value for E at each instant during the operation of the. engine. This value for A can be readily determined by measuring the distance, which the, piston 44 moves from the position it assumes when E approaches zero, i.e., when the plug 44 isaas far to the left as is possible. V v

The movement'of'the plug 44 can be measured in any of a variety of manners. -In-the device shown in'FIG. 1, however, plug movement is measured by apotentiometer arrangement, and values for X are either read directly or are automatically converted directly into values.

Referring to FIG. 1, a,linear potentiometer winding 58 is shown disposed within chamber. 4, the winding being supported by a'pairo'f fthreaded terminal posts60 and 62, one at each end thereof. "The posts 60 and 62 passv through openings" in the housingf2,.the openings each having electrical.insulatingelements 64 fitted therein, and are secured by nuts 66... A potentiometer slide 68 is secured to the end face of plugf44,- and includes a pair of resilentcontact arms, 'o'neof which rides on the winding'58 and the other of which rides on rod 40,

' said rod being constructed of a conductive material and serving as an electrical conduit for the potentiometer. A source of electrical current 70 is connected'between th two tenninal posts .60 and 62,. and an ammeter72 is connectedbetween rod 140, and the. terminal postf60; Thus, movement of plug 44 causes slide 68 to move along- :winding 58, causing a 'change'in theresistancebfjthe not permotfine calibrating adjustments to adjust the recirculating fiuid flow rate for accurate correlation with any specific setof scalar values {for E. A'secondernbod-iment of the invention is therefore illustrated in FIG. 2 which-overcomes thesesomewhat undesirable characteristics'of the simplified construction of FIG. 1.

" 1 Referring toFIG. L a/meter for use'v' vithautomotive vehicles and' the jlike is indicated at 73, and includes a housing 74' having therein an outlet chamber 76, an inlet .chamfber -7=8,*'and a. recirculating fluid outlet chamber '80.

.' The twoou-tlet chambers 76 land 80 havethreaded outlets:;82 and 84, respectively, in communication therewith,

"and a pair of threaded. in'lets'86'and' 88, connected with a fuel pump and the outlet of a positive displacement type recirculating -fluid pump 90, respectively, are in communication with inlet: cham ber '7 8."' The outlet .84 is connectedto the inlet of pump 90, and said pump is suitably connected-in the same manner as pump 56 to the power train of the vehicle on which the meteris installed.

The housing 74 has therein a pair of aligned cylindrical bores 92 and 94, [within whichv are respectively secured spaced apart tubular conduits .and 98 havingidentical internal dia metersa A rod 100, similar in construction to and mounted in thesamemanner as rod 40 extends concentrically lth rough conduits- 96 and 98, and a plug 102 having .acentra'l bore 104 therethrough is carried by said r-od. l a I .E

I The plug 102 includes a pair of spaced end portions and .108 having identical, relatively large diameters, and aJcent-ral, reduced in diameter connecting shaft 110.

l. A pairvof'deten ts 1-1-2on rod 100,1irnit the movement of circuit'fand' hence in the ,value of the current fflowing,

therethrough. Theelectnic current valuesforeach position of plug 44, and hence-for each value'ofX, areindi cated on meter 72', which may be calibrated either inunits" of length .or directly in valuesfor E. y The slide 68 may tend to create a small friction drag force -yvhich'tends to slightly impede the movement of plug 44. However, inmost applications'for theinven, tion, "and especially for automotive, use, the meter will a be positioned in close proximitytothe engine whose plug 102, andthe dimensional rel ationships .of the. latter with regard to the tubes 96 and 98 .are the same as t-he like relationships between plug 44..an-d its associated "eon: d-u ts 22 and 26 The plug endportions106and conduit '96,'define therebetween an annular flow channel 0', which ,is identical in ined-t0 an'annular'fiow channel R defined between plug end portion 108 and the tubular conduit 98.

1 The structure thus far described is similar in construction and, principal of operation tothe corresponding components of the embodimenti-llustrated inF IG. 1.-

The hOII SIHgJ74 -EIISO includes a cylindrical bore 114 I positioned parallel to bore 94, the two bores being of like length and having'their ends lying in, common planes. A Y tubular conduit 1l16 having 'anin tcrnal diameter identical efliciencyit'is'measu'ring. The constant' vibration -normall'y" inherent in engine operation will thus be trans? to that. of the conduits 9-6 and 98 is secured within said bore, and communicatesat its opposite end-s with cham- 9 bers 1 18 and 1-20 in the housing. The chambers 118 and 1 20 in turn are in communication with inlet chamber 78 and the recirculating fluid outlet chamber 80, respectively, so that fluid recirculated by the pump 90 flows in parallel through both conduit 1 16.

A cylindrical calibrating plug 122, having an external diameter identical to that of the metering plug end portions 106 and 108, is supported concentrically within tube 116 .by a threaded shaft 124 rigidly attached thereto, sa1d shaft projecting through a threaded bore 126 in the end wall of the housing 74 and being locked in position by a lock nu-t .126. Thus, a third annular flow channel A is defined between the plug 122 and tube 116, said channel having a cross-sectional area identical to that of the channels O and R. The length of the channel A, indicated in the drawing by the dimension C, can thus be precisely varied merely by first releasing lock nut 128 and then rota-ting shaft 124.

An examination of FIG. 2 will reveal that when the pump 90 is operating the same fluid, at the same temperature and with the'same viscosity, flows in parallel through both the channels R and A. Further, the flow rates through the lengths L and C in FIG. 2 will be inversely related to these lengths, and the same pressure differential between the ends thereof will exist for both channels.

From Equation 14 it is known that:

I E=M (14) In the device of FIG. 2 it is apparent that the length of the constant flow channel includes both the length C and the length L'. Thus, for the meter 73 Equation 14 may be rewritten as:

W here I E =the instantaneous operating efliciency for the meter As has been herein above described, the meter of the invention is .best calibrated when it is reading at midscale, with the length of the two flow channels around the metering plug being identical, This relationship for the embodimentof FIG. 2, based on Equation 16, may be expressed as: I I I Rearranging and inverting Equation 17, it can be shown that: l

n-M, (From Equation 17, it is readily seen that for any given pump 5'0 having a fixed value for M the value of E may be easily correlated over a wide range merely by adjusting the length C of the flow channel A. Thus, the same meter 73 and pump 90 can beinstalled on any one of a number of. automobiles or the like, and may be correlated to the expected range of E; values thereof merely by adjusting the calibrating plug 122.

The desired setting for the calibrating plug for any specific M at any desired scale reading IE at which X equals L is easily obtainable from Equation 18, it only being necessary that M be less than the value of E when X and L are equal.

, The operation of the meter 73, once calibrating plug 122 has been properly adjusted, is substantially the same as described for the meter shown in FIG. 1.

19 Values for E are indicated by the length X, which is measured in the meter .73 by a potentiometer arrangement 130 identical in construction and operation to the potentiometer arrangement utilized for measuring the length X in FIG. l.

When the meter of FIG. 1 is utilized in an automobile, with the outlet 14 connected to the fuel inlet or carburetor of the automobiles engine, the flow within chamber 4 and through channel 0 may be caused to pulsate because of a chattering action on the part of the carburetors float. When this condition, which may also happen in other situations, occurs, the metering, plug 44 tends to oscillate rapidly back and forth in a jerking movement. This undesirable effect is substantially eliminated in the meter of FIG. 2.

Referring again to FIG. 2, the housing 74 is seen to include a chamber 132 in alignment with chamber 76 and within which is mounted the potentiometer winding of the assembly 130. A wall 134 separates the chambers 132 and 76, and has a circular opening 136 therein in alignment with the tube 96. The plug end portion 106 is of sufficient length to extend through the opening 136 and into the chamber 132 even when the plug is shifted to the right as far as is possible, and the diameter of the opening 136 is slightly greater than that of said piston end portion whereby to define a clamping orifice.

As is apparent, it is the effect of pressures P acting on the ends of the plug that cause it to move. The pressure P acting on the left end of the plug is that of the fluid contained in damping chamber 132, which fluid must. move into and out of said chamber through the damping orifice defined by the opening 136. Under relatively slow changes in fluid pressure the pressures within chambers 76 and 132 quickly equalize. However, any rapid pressure changes which might cause the plug 106 to chatter are damped out by the resistance offered to rapid fluid flow by the damping orifice; thus, the plug 106 is not subject to oscillations caused by rapidly pulsating flow in outlet chamber 76.

In the event the damping orifice is not sufliciently effective in controlling the effects of plusating fluid flow, this invention also contemplates other means for stabilizing the rate of fluid flow from outlet chamber 76. For example, a closed plastic bag enclosing air or an inert gas, may be disposed in the flow path from the meter to the carburetor. All flow equalizing devices must be sparingly utilized, however, lest short duration changes in actual miles per gallon rates. be smoothed over and not be recognized and reported by the meter. The extent of their proper use will depend on how much pulsation characterizes the flow rate to any particular carburetor.

Obivously, the flow damping device of FIG. 2 may also be utilized with the meter of FIG. 1. In addition, it must be remembered that the drawings are only schematic, and that the other possible arrangements of the components of the invention are possible within the teachings hereinabove presented.

As has been mentioned hereinabove, While the invention has been thus far described with relationship to gasoline or similar fiuid fuel operated motor vehicles, it should not be considered as being limited to such use. Further, the meter may be utilized in situations where the normal working fluid is unsuitable for the meter because of its viscosity or some other reason, or where no working fluid is normally available; in either of these instances the meter is supplied with a suitable working fluid, one portion of which is pumped through the adjustable flow channel at a rate proportional to the inputof a device, and another portion of which is recirculated through the other flow channel by a recirculating pump connected to the output of said device.

By way of example only, the manner in which the invention may be utilized with a device where no working fluid is available will bedescribed with a battery powered, .electric motor propelled ves For use' with such a vehicle the inlet 16 of the {meter shown in FIG. 1 'would be connected through 'a fluid pump to a fluid reservoir. The reservoir would contain a working fluid of pa sl litable viscosity, andvthe fluid 7 in 'connection having a fluid fuel engine,

including a housing having an inlet port means therein. connected with .a source of fluid fuel, and 'a pair of flow channels in communication at oneendithereof with said inlet means, the other end of one of said flow channels being in communicationwith the fuel inlet of said engine, means connected-with said housing inlet portmeans and the othertend ofthe'other of said flow'channels tor recirculating fluidafuel through pump would be connected with the control'circuitry- V V theratio of said recirculating fluid fuel flow, to the fluid of the electric vehicle to pump said fluid into the meter at a rateproportional to the amount of electric power supplied to the motors; In this instanceythe fluid'outlet 14 would merely be connectedto return the working'fluid to said reservoir. I 1

p The recirculating pump 56 would again be connectedi to the-vehicle Lwheels-sothat it operates at a rateproportional to' the torwardtravel of the vehicler Thus, a portion of the working fluid would be recirculated through channel R. ata rate proportional-to the mileage traveled; The position-of-the metering plug 44 will 7 thus indicate the efiiciency of the; electric vehicle in terms of miles }per watt, or some other} suitablei compara; tivebasis.-

Obviously, many teachings. "It; is thereforeto be, understood lthatgwithin modifications and variations -of the present invention are possible in 'the;light"of"the;above said other flowchannel at a .rate proportional to the instantaneous speed of said vehicle, fluid pressureresponsive meansin said'housing for comparing andindicating fuel flow through said one flow channel, whereby to measure'the operating efficiency of said vehicle, and

7' housing defining an adjustable in lengthjflow} channel, arranged in parallel' with saidiiotheli.flowchannels v.

imeasunng andt-indrcatingthe operating' efficiency of a 6: An 'efiiciencyi meter apparatusffor continuously l motor svehiclez havinga fluid [fuel engine, including a the scope of the appendedclaimstheinvention mayjbe practiced otherwise than as specifically described: What is claimed is:

rates being proportional to the output of said apparatus,

comprisingv a housing, a pair of aligned, spaced [boresjf twithin said housing, a plug member including a relay tively long end portion, a relativelyfshont end portion, and a shaft portionof smaller diameter than and connecting 'said-endaportions, .said end portions'being of smaller diameter than said boressand each being disposed within one of saidbores'for'translational'moyementwith respect I thereto, saidlongend. portion and its assoeiated'bore defining: a'flow channeltwhich variesin length as said plug member 'is..translated, andsaid'sh'ortzend portionand, its associated bore defining a flowichannel which main tains a fixed length Las said .plug member is translated,

and said housinghaving' an inlet port means positioned tor continuouslyq comparing and indicating; the ratio between two rates of fluidflow; one of: said fluid flow rates beingv proportional to the input of-an apparatus and the other {of said-fluid flow housing having atpair"of spacedyaligned bores therein of identical:.;cross sectional area, .said housing also having va pairofinlet plorts positionedbetween and incom: munication withjsaidjspaced'bores, and a painofgoutlet ports, one at the end of each said bore remote from said inlet ports, a meteringplug; including a pair of identical in cross-sectional area end portions and a connecting i 3 shafthavingfasinaller.crosssecticnal area than said end portions, one of' saidend portions"being-substantially longer than the other thereoftand both of s'aidi'end p'or-i a tions being substantially smaller in cross-sectional area. than said bores, means for-mounting said plug concentrically within said ,bores 'for f'translational movement, the longer plug endbeingi-received withinone of said bores and defining-therewith a variable length flow channel and the shorter plug, end being receivedwithin the other of said bores and defining therewith afi xed' length ,flow channel, one of saidiinlet ports being connected witha source Qf fluid fuel: and the'outle't port associated with said variable length-flow channel being connectedwith t the fuelinletot s aid engine, pu mp means connected between theother of 'said inlet p orts and'the other outlet port and arranged to recirculate a portionof said flnid. fuel through said fixed flow channel ata rate' proportional tothe instantaneous/speed ofisaid vehicle, and means connected to said housing for measuring andremotely in saidplug member will be translated in response to .differential, fluid pressure until the forces exerted; thereon by said twol-fluid flows balance, theilength of said, variable length flow channelthen being anindication of said'ratio. v a 1 2, An efliciency metergasrecited' in claim 1, including additionally means connected to said housinggfor meas- 1 Wi an r lyi at g; the length of said variable flow channel, y t

3. An efliciency meter as: recited in claim including additionally means in said; housing defining ajthird, ad-

justablein. length flowchanneh'said thirdflqw channel, being arranged in parallelwith said" fined; length; flow channel forvcalibratingz said meter 1 "4. :An efliciency-rneter: as recited 1n claim 1 including j additionally means attached'to said housingan'd associated withsaidIplug for-damping rapid changes in said: rates 5. An- 'eflicien'cy meteriapparatus for "continuously; measuring the operating efficiency of a motor vehicle dic'ating thejlength of said variable flow channel;

7. An efliciency meter apparatusjas recited in clairn fi, including additionally orifice means in 'said' housing and arranged to cooperate with said plug for damping sudden changes in the pressure, Qff flllid flowing, therethrough. f8. Anefficiency meten'apparatus as recited in claim 6,

rate, passesfrom said ,inlet, through said fixed channel 1 including additionally adjutab1e inlgngth calibration flow channel in said housing arranged in :parallel with said fixed flow channel. I

a 9. An efiiciency meterapparatus as recited in claim 8, wherein ,said calibration flow channel has a cross-sectional area identical, to. that of, said fixed flow channel. 10; An efficiency meterappa'ratus as recited inclaim 6, wherein said 1 last mentioned meansjincludes a poten- ;Iwith.in saidhousing, and, connected 7 7 Li An .efliciencymeter apparatus as .'recitedin claim 6,1whereinfsaid metering plug has a density substantially identical to the. mean density offthe fluid flowing through aid er iqpaiatu t; a

l 7' keferencesi Cited the Examiner] UNITEDSTATESVYPATENTSI I 5 nrcnAnniczounrssnn, PrimnryExcminer. 

5. AN EFFICIENCY METER APPARATUS FOR CONTINUOUSLY MEASUREING THE OPERATING EFFICIENCY OF A MOTOR VEHICLE HAVING A FLUID FUEL ENGINE, INCLUDING A HOUSING HAVING AN INLET PORT MEANS THEREIN CONNECTED WITH A SOURCE OF FLUID FUEL, AND A PAIR OF FLOW CHANNELS IN COMMUNICATION AT ONE END THEREOF WITH SAID INLET MEANS, THE OTHER END OF ONE OF SAID FLOW CHANNELS BEING IN COMMUNICATION WITH THE FUEL INLET OF SAID ENGINE, MEANS CONNECTED WITH SAID HOUSING INLET PORT MEANS AND THE OTHER OF THE OTHER OF SAID FLOW CHANNELS FOR RECIRCULATING FLUID FUEL THROUGH SAID OUTER FLOW CHANNEL AT A RATE PROPORTIONAL TO THE INSTANTEOUS SPEED OF SAID VEHICLE, FLUID PRESSURE RESPONSIVE MEANS IN SAID HOUSING FOR COMPARING AND INDICATING THE RATIO OF SAID RECIRCULATING FLUID FUEL FLOW TO THE FLUID 